marshmallow-sqlalchemy

Release v0.25.0 (Changelog)

SQLAlchemy integration with the marshmallow (de)serialization library.

Declare your models

import sqlalchemy as sa
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import scoped_session, sessionmaker, relationship, backref

engine = sa.create_engine("sqlite:///:memory:")
session = scoped_session(sessionmaker(bind=engine))
Base = declarative_base()


class Author(Base):
    __tablename__ = "authors"
    id = sa.Column(sa.Integer, primary_key=True)
    name = sa.Column(sa.String, nullable=False)

    def __repr__(self):
        return "<Author(name={self.name!r})>".format(self=self)


class Book(Base):
    __tablename__ = "books"
    id = sa.Column(sa.Integer, primary_key=True)
    title = sa.Column(sa.String)
    author_id = sa.Column(sa.Integer, sa.ForeignKey("authors.id"))
    author = relationship("Author", backref=backref("books"))


Base.metadata.create_all(engine)

Generate marshmallow schemas

from marshmallow_sqlalchemy import SQLAlchemySchema, auto_field


class AuthorSchema(SQLAlchemySchema):
    class Meta:
        model = Author
        load_instance = True  # Optional: deserialize to model instances

    id = auto_field()
    name = auto_field()
    books = auto_field()


class BookSchema(SQLAlchemySchema):
    class Meta:
        model = Book
        load_instance = True

    id = auto_field()
    title = auto_field()
    author_id = auto_field()

You can automatically generate fields for a model’s columns using SQLAlchemyAutoSchema. The following schema classes are equivalent to the above.

from marshmallow_sqlalchemy import SQLAlchemyAutoSchema


class AuthorSchema(SQLAlchemyAutoSchema):
    class Meta:
        model = Author
        include_relationships = True
        load_instance = True


class BookSchema(SQLAlchemyAutoSchema):
    class Meta:
        model = Book
        include_fk = True
        load_instance = True

Make sure to declare Models before instantiating Schemas. Otherwise sqlalchemy.orm.configure_mappers() will run too soon and fail.

(De)serialize your data

author = Author(name="Chuck Paluhniuk")
author_schema = AuthorSchema()
book = Book(title="Fight Club", author=author)
session.add(author)
session.add(book)
session.commit()

dump_data = author_schema.dump(author)
print(dump_data)
# {'id': 1, 'name': 'Chuck Paluhniuk', 'books': [1]}

load_data = author_schema.load(dump_data, session=session)
print(load_data)
# <Author(name='Chuck Paluhniuk')>

Get it now

pip install -U marshmallow-sqlalchemy

Requires Python >= 3.6, marshmallow >= 3.0.0, and SQLAlchemy >= 1.2.0.